OF COURSE!!!
Well for me it is.
Piling on moisturizer then oil is just overkill sometimes. Especially for some products.
For example, I can use Qhemet's Olive Creme Detangler and need NO OIL. But for some reason her Heavy Cream make me want to top it off with some oil.
I think you have to just use you discernment based on how your hair feels and if it maintains moisture or not.